Officials say thousands - maybe as many as 5,000 - of Philadelphia row homes, built during its industrial heyday, are considered unsafe and often vacant.

Brenda Clayton's block has at least five abandon homes that attract rats and thieves.

"They stripped the pipes and all the stuff in the homes. It's horrible. There's nothing good about them, they need to be tore down" said Clayton of North Philadelphia. "Then we got an abandoned school at the end of the block so that's even worse."

The biggest worry for L&I is a building collapse.

"What we're looking at is how do we protect public safety," said Karen Guss, Licenses and Inspections.

L&I has 19 inspectors focused on dangerous properties.

It earmarks $9 million to demolish 600 of them a year.

To help to improve the odds of finding the most dangerous of buildings, it's turning to the city's Office of Innovation and Technology, which use aerial mapping efforts.

The near-term goal is to give inspectors overhead information they can't get from the ground. For example, a hole associated with a collapsed roof.

"That gives us information that tells us wow this building is in worse condition than we thought," said Guss.

Any building collapse could be dangerous, but some locations can be worse than others.

"It also tells us what else is around that building so we are more concerned about a building near a bus stop than a building in a vacant lot," said Guss.

Right now the system is a work in progress. Down the road it's hoped it will be able to predict troubles by making exact measurements of building roof lines.

"Look for significant drops in elevation and that's something that could be predictive," said Mark Wheeler, Office of Innovation and Technology. "We could do an analysis to find all these drops that tell us that's probably a collapsed roof."

The hope is technology will let inspectors get ahead of the curve when it comes to finding dangerous buildings so L&I can intervene before someone gets hurt.